PURPOSE: To realize a temp. sensor of an absolute explosion-proof type, by providing an optical fiber bending so as to follow the deformed shape of a temp. deformable member and the optical connectors mounted to both ends of the optical fiber.

CONSTITUTION: The title sensor is constituted by mounting a temp. deformable member 1 holding inherent different shapes by the change in temp. to be applied, an optical fiber 2 mounted to the temp. deformable member 1 along the deformable part thereof and bending so as to follow the deformed shape thereof and optical connectors 3 mounted to both ends of the optical fiber. Light is incident to the optical fiber from a light source through the optical connector 3 at one end thereof and the emitted light from the optical connector 3 at the other end is converted photoelectrically to detect the change in the quantity of light passing through the optical fiber 2. As the temp. deformable member 1, for example, a shape memory alloy is used. By this method, an absolute explosion- proof type temp. detection sensor can be realized.